1. Field of the Invention
The invention relates to a device and a method for ejecting ink droplets to record an image on a recording medium.
2. Description of Related Art
A known image recording device, e.g., an inkjet printer, records an image on a sheet of recording medium while the sheet is conveyed intermittently. In a known inkjet printer, a sheet is conveyed onto a platen while being pinched between a pair of opposed rollers. After the sheet reaches the platen, the pair of rollers are driven intermittently. Each time the sheet is conveyed by a predetermined sheet feed distance and stopped, a recording head moves in a direction orthogonal to a sheet conveying direction and ejects ink droplets onto the sheet. As sheet feed and ink ejection are repeated, a desired image is formed on the sheet from a leading edge to a trailing edge thereof.
In the known inkjet printer, sheet cockling may occur. Sheet cockling is a phenomenon where ink permeates fibers of the sheet and expands the fibers such that the sheet is curled and undulated. If sheet cockling occurs, a distance between the sheet and the recording head may fluctuate during image recording, and the accuracy in image recording may deteriorate. The deformed sheet may contact the recording head or cause a leading edge of the sheet to deviate from the conveying path and may cause a sheet jam.
A known inkjet printer, e.g., the printer described in Japanese Laid-Open Patent No. 2004-237506, comprises a recording head, a platen opposed to the recording head, a pair of rollers disposed upstream of the platen, and a pair of rollers disposed downstream of the platen. When an amount of ink which causes deformation of a sheet is ejected from the recording head onto the sheet while the sheet is pinched by the upstream rollers, the sheet is conveyed till a leading edge of the sheet is pinched by the downstream rollers. Then, the sheet is held by the upstream rollers and the downstream rollers for a predetermined amount of time to reduce deformation of a leading edge side of the sheet.
In the known inkjet printer, the leading edge of the sheet is pinched by the downstream rollers. However, when the sheet, e.g., a sheet having fibers running widthwise, is prone to suffer from cockling, the leading edge may be deformed greatly before the leading edge reaches the downstream rollers, and the deformed leading edge may collide with the downstream rollers and cause a sheet jam. When the distance between the recording head and the sheet is relatively small, the deformed sheet may contact the recording head and cause deterioration of the recorded image or damage to the sheet.